Axial piston machine with offset positioning element and cam disk for such an axial piston machine

ABSTRACT

The invention relates to an axial piston machine ( 1 ) comprising a housing ( 2 ) in which a drive disk ( 7 ) and a cylinder block ( 12 ) axially disposed next to it are received so as to be rotatable relative to each other about longitudinal center axes ( 11, 13 ). These axes run obliquely at an angle (W 1 ) relative to each other in an oblique axis plane (E). A cam disk ( 18 ) is disposed on the front of the cylinder block ( 12 ) facing away from the drive disk ( 17 ) and is supported on the housing ( 2 ) by means of a positioning device ( 19 ) with positively engaging positioning elements ( 19   a,    19   b ). A guide element ( 21 ) having a guide center axis ( 22 ) running coaxially to the longitudinal center axis ( 13 ) of the cylinder block ( 12 ) is disposed on the side facing the cylinder block ( 12 ). In order to provide for a simple construction and to allow for a step-wise modification of the throughput, the positioning element ( 19   b ) disposed on the cam disk ( 18 ) is set off in the oblique axis plane (E) at an angle to the guide center axis ( 22 ). The cam disk ( 18 ) can be mounted in a second position, rotated relative to the guide center axis ( 22 ) by approximately 180°, in which the positioning elements ( 19   a,    19   b ) are also functionally linked.

The invention relates to an axial piston machine and a cam disc for suchan axial piston machine.

An axial piston machine of this type is, for example, disclosed in DE100 30 147 A1 and namely both as an axial piston machine with constantthroughput volume and with variable throughput volume.

The throughput volume is varied in this known construction by thecylinder drum and the cam disc being pivoted in the oblique axis planecontaining the centre axes of the drive disc and the cylinder drum. Tothis end a driving connection with positioning elements positivelyengaging in one another can be provided between the cam disc and thehousing or a control block in place of a housing wall. In thisconnection, the pivoting takes place in a circular arc shaped guidecurved about the intersection of the centre axes and extending in theoblique axis plane and in which the cam disc is pivotally guided.

The object of the invention is to design an axial piston machine and acam disc for such an axial piston machine, ensuring a simpleconstruction, such that a step-wise variation of the throughput volumeis possible.

The invention is based on the recognition that, instead of pivoting in aguide, the cam disc can be adjusted by an offset of the cam disc whichcan be achieved by rearranging the cam disc by rotating it by 180 DEGabout its guide centre axis. As a result, two positions of the cam discare produced, arranged offset to one another in the oblique axis planeand in which the angle between the centre axes of the drive disc and thecylinder drum is variable and therefore the throughput volume isvariable.

In an embodiment, the positioning element arranged on the cam disc istransversely offset relative to the guide centre axis in the obliqueaxis plane, the cam disc being optionally able to be installed in twopositions offset by 180° to one another.

In an embodiment, the positioning element arranged on the cam disc isarranged offset relative to the guide centre axis in the oblique axisplane.

The two embodiments according to the invention allow a lateraldisplacement of the cam disc which leads to variable volume adjustmentdepending on the oblique axial arrangement. In this connection, one ofthese two volume adjustments can optionally be carried out by the camdisc being rearranged by rotating it by 180° or the cam disc alreadybeing specifically installed during the initial installation in one ofits two positions. As a result, the desired throughput volume can beconsidered during installation and initial installation of the axialpiston machine. The size of the throughput volume variation can bedetermined by the size of the offset dimension, by which the positioningelement arranged on the cam disc is offset relative to the guide centreaxis.

The two embodiments according to the invention are suitable for variablethroughput volumes which can be set. As a result it is possible, whenassembling the axial piston machine, to establish whether the throughputvolume is to be larger or smaller than a desired throughput volumerange.

An offset of less than 10°, in particular of approximately 3°, allowsthe creation of large flow cross-sections for the flow channels in thecam disc and in the connecting part. Thus flow losses can be reduced andthe speed stability and the efficiency of the axial piston machine canbe improved.

The invention is also suitable for use in combination with an axialpiston machine of which the throughput volume can be set by pivoting thecam disc by means of an adjustment device. With this combination, theembodiment according to the invention firstly allows a displacement ofthe adjustment range to a minimum direction of, for example, 0° or amaximum direction of, for example, 32° and secondly an increase of theadjustment range when the cam disc is positioned, such that theadjustment path is increased by the offset.

The embodiment according to the invention is thus suitable both for suchaxial piston machines, in which the cam disc cannot be displaced in itsinstalled position and for such axial piston machines in which the camdisc can be displaced for the purpose of altering the throughput volumein a circular arc shaped guide curved about the intersection of thecentre axes of the drive disc and the cylinder drum. In the lastdescribed embodiment, the throughput volume can be varied steplessly inthe region of the guide. In this embodiment the embodiment according tothe invention is preferably suitable for varying the throughput volumein the region of the maximum limit of the adjustment range.

The aforementioned advantages can also therefore be achieved when theembodiment according to the invention is combined with an axial pistonmachine, of which the adjustment range is smaller than the increasedadjustment range which can be achieved by the offset of the cam disc. Ifthe adjustment device of the axial piston machine is designed, forexample, for an adjustment range of 0° to 26°, then by a specificinstallation or rearrangement of the cam disc according to theinvention, the pivoting range can moreover be set from 0° to 26° in itsone position and in the other position an adjustment range increased bythe offset dimension can be set, which however ends before the minimumsetting 0°. With an offset dimension of, for example, approximately 3°,in the latter case an adjustment range of 6° to 32° can be set.

A raised portion on the side of the cam disc facing the cylinder blockis suitable as a guide element for the cylinder block and whichcooperates positively with a correspondingly formed front face of thecontrol block. In an axial piston machine with a rotatably mountedcylinder block, namely a so-called cylinder drum, arotationally-symmetrically curved design of the guide element and of thefront face of the cylinder drum cooperating positively therewith isrequired.

As a positioning device for positioning the cam disc, a positiveengagement known per se between a recess and a pin held therein is wellsuited to ensure a simple and inexpensive construction.

The invention will be described hereinafter with reference toadvantageous designs of an embodiment, in which:

FIG. 1 is an axial piston machine according to the invention withvariable throughput volume in axial section;

FIG. 2 is a portion of the axial piston machine in an altered positionrelative to its throughput volume;

FIG. 3 is an enlarged view of a substantial region of the axial pistonmachine in the position according to FIG. 1;

FIG. 4 is a front view of a cam disc of the axial piston machine;

FIG. 5 is a rear view of the cam disc;

FIG. 6 is the region identified by X in FIG. 3 of the axial pistonmachine in a modified embodiment.

In the axial piston machine shown by way of example and denoted as awhole by 1, the axial piston machine is of oblique axis construction.This construction comprises a closed housing 2, with a pot-shapedhousing part 3, of which the housing interior 4 can be releasably closedby a so-called connecting part 5 which is screwed by means of screws 6shown in outline to the free edge of the housing part 3. In the housing2 a drive disc or drive shaft 7 is rotatably mounted which passesthrough the one base wall 3 a of the pot-shaped housing 3 in a throughhole 8 and is rotatably mounted therein, for example by means of rollerbearings 9 a, 9 b which are seated in the through hole 8.

In the present embodiment, in which the drive disc is rotatably mounted,the longitudinal centre axis 11 of the drive disc 7 is simultaneouslyits rotational axis. Axially mounted in the vicinity of the drive disc 7is a cylinder block 12 in the housing interior 4 with a longitudinalcentre axis 13 which extends obliquely relative to the longitudinalcentre axis 11 of the drive disc 7 in an oblique axis plane containingthe two longitudinal centre axes 11, 13, so that the longitudinal centreaxes 11, 13 include an acute angle W1 which is open toward the sidefacing away from the drive disc 7. The intersection of the longitudinalcentre axes 11, 13 is denoted by 14.

In the cylinder block 12, a plurality of piston bores 15 are distributedon its cross-section and arranged parallel, for example, relative to thecentre axis 13 and which open out in the direction of the drive disc 7and in which pistons 16 are mounted which can be displaced to and froand of which the ends facing the drive disc 7 are supported in auniversally pivotal manner on the drive disc 7. To this end, sphericalsegment bearings 17 are provided in the embodiment between the pistons16 and the drive disc 7.

On the front face of the cylinder block 12 facing away from the drivedisc 7 a cam disc 18 is arranged which is supported on the housing 2 bya positioning device 19 and on its side facing the cylinder block 12comprises a guide element 21, with a guide centre axis 22 for thecylinder block 12. The guide centre axis 22 extends transversely to thecam disc 18 and in the centre region of the cam disc 18, as well ascoaxially to the longitudinal centre axis 13 of the cylinder block 12.This is supported in the direction of the cam disc 18 by guide surfaces23 a, 23 b bearing against one another and by the guide element 21 onthe cam disc 18, transversely to the guide centre axis 22.

By means of a relative rotation between the drive disc 7 and thecylinder block 12 the pistons 16 are pushed to and fro due to thepresence of the axial angle W1 and, depending on the rotationaldirection, the pistons 16 drawing in fluid on the one side of thelongitudinal centre axis 13 and displacing it on the other side. Thusthe fluid flow flows from an inlet, not shown, through control channels25 in the cam disc 18, arranged symmetrically on the two sides coaxiallyto the guide centre axis 22, through channels 26 in the connecting part5 extending toward the control channels 25 and through channels 27 inthe cylinder block 12 extending from the control channels 25 toward thepiston bores 15, to an outlet, not shown, also arranged on theconnecting part 5.

In the embodiment the guide element 21 is formed by the guide surfaces23 a, 23 b, preferably spherical sector-shaped, being curvedconcentrically to the guide centre axis 22 and the longitudinal centreaxis 13 and namely curved in a concave manner on the front face of thecylinder block 12 and curved in a convex manner on the opposing frontface of the cam disc 18, so that the guide surface 23 a defines a raisedand convex guide element 21, as is known per se.

The positioning device 19 is formed by a positioning element 19 a on theconnecting part 5 and a positioning element 19 b cooperating therewithon the cam disc 18. The positioning elements 19 a, 19 b cooperatepositively, such that a movement directed transversely to the guidecentre axis 22 and a movement of the cam disc 18 away from the cylinderblock 12 is positively locked by the positioning device 19 on theconnecting part 5. The positioning elements 19 a, 19 b engage in oneanother along an engagement axis 19 c. An embodiment of the positioningelements 19 a, 19 b which can be easily assembled and disassembled isthen achieved, if it can be assembled and disassembled by an assemblingand disassembling movement of the cam disc 18 and the connecting part 5directed along the guide centre axis. In such an embodiment thepositioning element 19 b on the cam disc 18 is accessible to thepositioning element 19 a on the connecting part 5 from the connectingface, on which the connecting part 5 is located.

In the embodiment the positioning element 19 b is formed on the cam discby a recess open from, and therefore accessible from, the connectingpart 5 and in which a positioning pin protruding from the control part 5toward the cam disc 18 is held with slight motional clearance. In thisconnection, the positioning device 19 is constructed such that thecentre axis 19 c of the positioning device 19 oriented transversely tothe cam disc 18, is laterally offset relative to the guide centre axis22 in the oblique axis plane E containing the two centre axes 11, 13.The corresponding offset dimension a is produced by the offset angle W2.As a result, the positioning element 19 a is also laterally offsetrelative to the guide centre axis 22 by the offset angle W2. The offsetangle W2 is smaller than approximately 10° and is preferablyapproximately 3°.

The positioning device 19 further comprises a bearing face 19 d on theconnecting part 5 facing the cam disc 18. The cam disc 18 rests with onebearing face 18 a on its front face facing the connecting part 5 on thebearing face 19 d and is thereby supported on the side facing away fromthe cylinder block 12.

The positioning device 19 is moreover constructed such that the cam disc18 can be installed into an offset position shown in FIG. 2 from theoffset position shown in FIGS. 1 and 3 and in which it is rotated by180° about the guide centre axis 22, and vice versa. Rearranging the camdisc 18 into the positions shown in FIGS. 1 and 2 leads to a lateraloffset of the cam disc 18 and the cylinder block 12 guided thereon, thisoffset being double the size of the offset a produced by the offsetangle W2.

The axial piston machine 1 disclosed thus far can therefore be assembledby installing the cam disc 18 in a specific assembly position or byrearranging the cam disc 18 into positions rotated by 180°. In thesepositions of the cam disc 18 the axial piston machine 1 can be set totwo throughput volumes of variable sizes and can be adjusted in onestep.

In the embodiment shown, the cam disc 18 can be laterally pivoted to andfro and fixed in addition to the aforementioned positions in a pivotingguide 31 extending parallel to the oblique axis plane E, the pivotingguide 31 being curved about the intersection 14 of the longitudinalcentre axes 11, 13. Moreover, an adjustment device 32 is provided, bymeans of which the cam disc 18 in the rotating guide 31 can besteplessly adjusted to and fro in the oblique axis plane E between aminimum position, for example with a pivoting angle of 0° and a maximumposition, for example with a pivoting angle of 26° and fixed in therespective pivoting position.

In the embodiment the pivoting guide 31 is formed by a guide groove 31 ain the wall of the connecting part 5 facing the housing interior 4, thebase of the guide groove 31 a being formed by the bearing surface 19 dand being curved in a concave manner about the intersection 14 andforming a curved guide and bearing surface 19 d, on which the cam disc18 slideably rests with its correspondingly convex curved bearingsurface 18 a. The adjustment device 32 is moreover incorporated in theconnecting part 5 and, for example, formed by an adjusting slider 32 awhich can be specifically displaced hydraulically transversely to theguide centre axis 22 and to and fro in a slide guide in the oblique axisplane E and can be fixed in the respective setting. The connecting part5 is arranged obliquely relative to the centre axis 11 in the obliqueaxis plane and with the centre axis 11 includes an acute angle W3 whichcorresponds to half the angle of the pivoting angle region and in theembodiment is approximately 16°. In this connection, W3=16° for the twoexemplary adjustment ranges 0-26° and 6-32°.

The positioning element 19 a arranged on the connecting part 5 isfastened in the embodiment to the adjusting slider 32 a and can bedisplaced to and fro therewith in a corresponding free space 34 andslot, the cam disc 18 being driven by means of the cooperation of thepositioning elements 19 a, 19 b. In order to ensure positioning in theoffset oriented transversely to the guide centre axis 22 in the obliqueaxis plane E, in spite of the variable moving directions between thepositioning elements 19 a, 19 b (straight, curved), the pin-shapedpositioning element 19 a plunges with a circular rounded positioninghead 19 e into the recess 19 f in the cam disc 18 forming the counterpositioning part.

With such a steplessly variable axial piston machine 1, the embodimentaccording to the invention allows either a reduction or increase in thethroughput volume of the axial piston machine or a specific setting ofthe axial piston machine from the outset by a correspondingrearrangement or initial assembly.

A particular advantage of the embodiment according to the invention canbe seen by the embodiment according to the invention being restricted tothe design of the cam disc and therefore the embodiment according to theinvention is suitable for resetting the piston machine, without itsother parts having to be altered. Thus, for example by a correspondingoffset of the cam disc, the adjustment range of the adjustment devicecan be increased by the offset dimension, without it requiring itself acorresponding enlargement of the adjustment device. This becomes clearwhen one considers that in an adjustment device with an adjustment rangeof, for example, approximately 0 to 26° the embodiment according to theinvention retains this adjustment range in the one position of the camdisc and in the other position results in an adjustment range which isincreased by the offset dimension of the cam disc, but which ends at theoffset dimension before the zero point of the adjustment device. Evenwhen the axial piston machine is installed from the outset with only oneof the two pivoting angle regions, the two pivoting angle regions can beproduced with a high similarity of parts.

The end positions of the pivoting regions can be defined by stops A1,A2, which are adjustable and can be incorporated in the connecting part5 as end stops for the adjusting slider 32 a. In the embodiment, aminimum stop A1 and a maximum stop A2 respectively formed by anadjustment screw 35 which passes through the peripheral wall of thehousing 2 in a threaded hole 36, approximately in the oblique axis planeE, protrudes into the housing interior 4 and can be rotated externallyby a rotary tool which can be applied to a rotatable engagement member,for example a slot 37 and can be fixed, for example by means of a locknut 38.

In the aforementioned embodiments the cam disc 18 is non-displaceablypositioned in each pivoting position relative to the cylinder block 12in the pivoting plane E. Thus between the cam disc 18 and the cylinderblock 12 a positioning device 41 acts which positions these two partsnon-displaceably on one another in the pivoting plane E. Thispositioning is carried out by the convex form of the cam disc 18 in thepivoting plane E and the concave form of the cylinder block 12.Therefore, the cam disc 18 is able to drive the cylinder block 12 whenit is displaced in the pivoting plane E, the positioning device 41acting as a drive device. The guide element 21 thus allows the rotationof the cylinder block 12 during the positioning.

This positioning device 41 is prone to an effective clamping actionbetween the cam disc 18 and the cylinder block 12 due to the relativelyslight arcuate form of the guide surfaces 23 a, 23 b.

It is therefore advantageous to stabilise the positioning device actingbetween the cam disc 18 and the cylinder block 12, such that theaforementioned clamping action and greater wear and tear and increase intemperature resulting therefrom can be reduced or prevented.

In the embodiment according to FIG. 6 the positioning device 41 isformed by an additional pin connection acting between the cam disc 18and the cylinder block 12, with a positioning pin 42 which is held in anappropriate manner respectively in positioning recesses 42 a, 42 b inthe cam disc 18 and in the cylinder block 12 and in addition passesthrough the gap 31 b therebetween. Moreover the pin portions 42 c, 42 dof the positioning pin 42 held in the positioning recesses 42 a, 42 bare offset to one another and cranked by the offset dimension a and theangle W2 and one or both of these pin connections can be installed inthe positions of the cam disc 18 rotated by 180°. The positioningrecesses 42 a, 42 b and the pin portions 42 c, 42 d preferably comprisea round cross-section. Due to the offset a the positioning pin 42 is,relative to the cam disc 18, unrotatably mounted in the cam disc 18. Inthe transitional region 42 g between the pin portions 42 a, 42 b thepositioning pin 42 can comprise side portions extending obliquely, whichpreferably are convex and concave and merge with the pin portions 42 c,42 d, as the drawing shows. The positioning recess 42 b forms a rotarybearing 40 for the cylinder block 12. This can be a roller- or frictionbearing which can comprise a sliding bushing 12 a fastened to one of therotary bearing parts.

In the embodiment according to FIG. 6 the positioning recess 19 b isarranged in the pin portion 42 c, it being adapted relative to itscross-sectional form and size to the cross-sectional size and form ofthe positioning element 19 a and able to be formed by a blind hole openon the front face. The positioning recess 19 b is preferably formed by alongitudinally extending channel and open toward a guide hole 15 areceiving a centre guide pin 16 a. As a result, the lubrication of thepositioning elements 19 a, 19 b is improved.

Furthermore, the positioning elements 19 a, 19 b can be constructed asin the embodiment according to FIG. 3, namely with a waist 19 h on thepositioning head 19 e and a recess widening 19 i on the perforated edgefacing the housing and connecting part 5, in order to increase theavailable pivoting region.

A sliding layer 44 arranged between the cam disc 18 and the cylinderblock 12 made from antifriction and/or hardwearing material can beformed by a disc which can be fastened to the cam disc 18, for exampleby soldering, welding or bonding. A hole 44 a penetrated by thepositioning pin 42 in the disc is large enough for the transitionalregion 42 g therein to have a free space in the two offset positions.

In the embodiment according to FIG. 6 the guide surfaces 23 a, 23 b,contrary to the aforementioned embodiment, are planar surfaces; they canhowever also be of spherical sector-shaped concave and convexconstruction, as is the case in the aforementioned embodiment.

The positioning recess 42 b and the pin portion 42 d are preferablyarranged coaxially to the longitudinal centre axis of the cylinder block12. The positioning recess 42 a and the positioning pin 42 c, as well asthe positioning recess 19 b, can be offset parallel relative to thelongitudinal centre axis 13 and the offset a. In the embodiment thepositioning recess 42 a, the pin portion 42 c located therein and thepositioning recess 19 b are arranged together, rotated by the angle W2relative to the longitudinal centre axis 19.

The rearrangement of the cam disc 18 can take place when the housingcover and connecting part 5 are removed, by the cam disc 18 beingremoved from the pin portion 42 c, rotated by approximately 180° aboutthe centre axis 13 and then replaced, or by the cam disc 18 being liftedwith the positioning pin 42 out of the positioning recess 42 b, rotatedby 180° approximately about the centre axis and again inserted into thepositioning recess 42 b. As far as possible, the rearrangement can alsotake place by the positioning pin 42 being rotated by 180 DEG in thepositioning recess 42 b.

1. Axial piston machine with a housing, in which a drive disc and acylinder block axially arranged in its vicinity are rotatably mountedrelative to one another about longitudinal center axes, which extendobliquely to one another by an angle (W1) in an oblique axis plane (E),a plurality of piston bores being arranged in the cylinder block and inwhich pistons are displaceably guided axially to and fro, of which thepiston ends facing the drive disc are supported in a universally pivotalmanner on the drive disc, on the front face of the cylinder block facingaway from the drive disc a cam disc being arranged which is supported onthe housing by a first positioning device with positively cooperatingpositioning elements and on its side facing the cylinder blockcomprising a guide element with a guide center axis extending coaxiallyto the longitudinal center axis of the cylinder block, wherein at leastone of said positioning elements is arranged on the cam disc offsettransversely to the guide center axis in the oblique axis plane (E) andthe cam disc is able to be installed in a further position rotated byapproximately 180° about the guide center axis, in which the positioningelements also cooperate, said cylinder block being positioned positivelyagainst relative displacement in the oblique axis plane (E) by a secondpositioning device, said second positioning device being formed by apositioning pin which is seated with a pin portion in a positioningrecess in the cam disc and is seated in a positioning recess of thecylinder block with a positioning pin offset in the oblique axis plane(E) by the offset (a).
 2. Axial piston machine according claim 1 whereinthe positioning element is offset relative to the guide center axis byan offset angle (W2) which is smaller than approximately 10°.
 3. Axialpiston machine according to claim 2, wherein the offset angle (W2) isapproximately 3°.
 4. Axial piston machine according to claim 1, whereinthe pin portion seated in the cylinder block is rotatably mounted in thecylinder block by a rotary bearing.
 5. Axial piston machine according toclaim 1, wherein the pin portion seated in the cam disc forms apositioning element for the first positioning device.
 6. Axial pistonmachine according claim 5, wherein the positioning element is formed bya positioning recess open on the front face.
 7. Axial piston machineaccording to claim 1, wherein between the cam disc and the cylinderblock a disc with a hole is arranged for the positioning pin whichpreferably is large enough so that in the offset position of the camdisc a transitional region of the positioning pin preferably extendingobliquely has a free space in the hole.
 8. Axial piston machineaccording to claim 1, wherein the positioning pin comprises an elongatethrough hole which preferably opens out into the positioning recess.